Callionymoidei

(Dragonets and relatives)

Class Actinopterygii

Order Perciformes

Suborder Callionymoidei

Number of families 2

Evolution and systematics

Members of this suborder include the Callionymidae (the dragonets) and the Draconettidae (deepwater dragonets). As with many other perciform fishes, members of this suborder likely radiated in the Eocene period. The systematic placement of this suborder begs further consideration as it has been placed under the nonperciform order Gobiesociformes (Gosline, 1970; Leis and Carson-Ewart, 2000), or linked to the family Gobiesocidae in a closely related suborder, the Gobiesocoidei, within the Perciformes (Helfman et al., 1997).

The Callionymidae consists of at least 17 genera and 156 species, although exact numbers vary because of two different and competing classifications proposed by T. Nakabo (1982 and 1983) and R. Fricke (1983). The Callionymidae genera include:

• Anaora (one species)
• Bathycallionymus (two subspecies)
• Callionymus (82 subspecies)
• Calliurichthys (one species)
• Dactylopus (one species)
• Diplogrammus (six subspecies)
• Draculo (five subspecies)
• Eleutherochir (one subspecies)
• Foetorepus (eight subspecies)
• Neocynchiropus (two subspecies)
• Paracallionymus (one subspecies)
• Paradiplogrammus (two subspecies)
• Progogrammus (one species)
• Pseudocalliurichthys (three subspecies)
• Repomucenus (10 subspecies)
• Spinicapitichthys (one species)
• Synchiropus (29 subspecies)

The Draconettidae consists of only two genera, Centrodraco (10 subspecies, but one with 2 subspecies) and Draconetta (one species).

Physical characteristics

The Callionymidae are relatively small, sometimes diminutive, usually elongate fishes, having both a depressed trunk and broad or depressed head. Most of these fishes are sexually dimorphic. Males tend to have larger body sizes and dorsal fins, greater fin ornamentation, and more distinctive color patterns. Dragonets usually have 2 dorsal fins, the first containing 1–4 spines, the second has only 6–11 rays; the last ray is divided at the base, as in the anal fin. Dorsal fins of males may also be large or high, and also have elongated rays. Dragonets also have relatively large pelvic and pectoral fins, with the former positioned forward of the latter. The anal fin has 4–10 rays. The shape of the caudal fin varies, but may be elongate or spade-like and include elongated rays. The preoperculum has well-developed spines and bars along the margin, but no opercular or subopercular spines are present. Dragonets are further distinguished by the presence of small gill openings, generally pore-like, positioned at the top of the head or along the upper flanks, with gill membranes that are united at the isthmus that separates the gills. Their bodies lack scales, but their lateral lines are quite well developed. Many species have color patterns well suited as camouflage, but others are brilliantly, if not spectacularly, colored. Some species, such as members of the genus Foetorepus, produce an acidic, bitter-tasting slime that covers their bodies and may serve as a toxic deterrent to predators.

Dragonet larvae develop quite rapidly, and most species are able to settle with a full compliment of fins at a small size. The larvae are denoted mainly by having a relatively large head, a short snout that lengthens with growth, a small, protrusible mouth placed terminally on the head, the presence of teeth only after settlement, a large eye that migrates dorsally with growth, and a gas bladder located anterior to the gut, which disappears in adults. The gills are free from the isthmus at first but become attached after the larvae undergo flexion. The bodies of dragonet larvae are heavily pigmented, with most of the pigment concentrated on the ventral, rather than dorsal, surface of the body.

The Draconettidae have small, elongated, and rounded bodies, pointed snouts, relatively large pectoral fins, and elongated pelvic fins. The gill openings are relatively broad. There are two nostrils on each side of the head. Scales are absent, but the body is distinguished by the presence of a grooved or vestigial lateral line that is well developed on the head. These fishes are also distinguished by having large eyes. There are two dorsal fins, with three spines on the first and 12–15 rays on the second. There are 12–13 soft rays on the anal fin. The operculum and suboperculum have single strong spines but these are absent on the preopercle. Their larvae are very poorly known. The body is elongate and compressed, the head is also compressed and is of moderate size, the snout is pointed, and the mouth is small and reaches as far as the anterior margins of the large, round eyes. The gas bladder is absent, and the fin elements are present in larvae at least 0.31 in (0.8 cm) long.

Distribution

The Callionymidae are found in tropical and warm temperate waters of the Atlantic, Indian, and Pacific Oceans. Species are found at either continental or insular localities, however most species occur in the Indo-Western Pacific. The Draconettidae share approximately the same broad distribution, but are limited to seamounts or deeper edges of continental shelves, and thus live at cooler water temperatures.

Habitat

Most members of the Callionymidae are found on coral pavement, rubble, sand, mud, or on other soft bottoms. Some species occur exclusively in corals, tide pools, or among rocks; however, others may be found among algae-covered rocks on flats or shorelines, or mangrove roots in brackish water. The two species of the genus Bathycallionymus occur on deep flats. Members of the family occur within a depth range of less than 39 in (1 m) at low tide to over 1,312 ft (400 m). Little is known about the habitats of the Draconettidae. They may likely be found in rubble and sand or amongst rocks along deep-slope edges or on top of seamounts.

Behavior

The behavior of dragonets has been studied for only a few species and, for these, most effort has been directed toward reproductive behavior. Males utilize their longer first dorsal fins for displaying in both male-male aggressive encounters, and male-to-female social and courtship interactions. Male body color may also be utilized, especially during courtship.

Virtually nothing is known about the behavior of members of the Draconettidae. Their large eyes likely aid them in movement, feeding, social interactions, and reproductive behavior in deep demersal habitats. The dorsal fins of males may be utilized for signaling, but their effectiveness under dimly lit conditions remains to be demonstrated.

Feeding ecology and diet

Callionymids and draconettids feed on small benthic invertebrates. Larger species, such as members of the callionymid genera Callionymus, Foetorepus, Repomucenus, and Synchiropus), feed upon correspondingly larger prey. Predators of dragonets and draconets are not well known, but it is likely that they are preyed upon by larger benthic-feeding or opportunistic predatory fishes.

Reproductive biology

Dragonets appear to be gonochoristic, with no evidence of sex change reported. Males maintain relative large home ranges compared to females and these may be defended territorially during periods of reproduction. Mating systems may consist of pairs or single-male dominated mating groups of two or more females. Some smaller, cryptically colored males may also be in these mating groups and will attempt to court and spawn with females, but will often fail because of aggressive interactions with the dominant male. Courtship and spawning typically commences prior to sunset for most species or possibly just after dawn in some species. A male will approach a female and display his erect fins to her, and, as if carrying her, will ascend with her a short distance into the water column, where pelagic eggs are released and fertilized. These eggs are spherical in the genera Calliurichthys and Repomucenus, and in Callionymus from the Atlantic Ocean. The mangrove dragonet (Paradiplogrammus enneactis), and perhaps others in this genus, produces a buoyant egg mass that later breaks up prior to hatching. Spawning may be seasonal, depending upon latitude and water temperature, and may demonstrate one or more peaks during an annual cycle. Serial spawning, with the daily production of eggs during the season, has been suggested for some species. Smaller females of some species with bimodal spawning seasons may defer reproduction until the second season (late summer or autumn).

Next to nothing is known about the reproductive biology of the Draconettidae. Both the spawning mode and eggs are unknown. Owing to their close relationship with the Callionymidae, they are sexual dimorphic, with males being larger than females. They are not likely to be hermaphroditic. Spawning is probably paired and pelagic, with a rapid, short ascent into the water column where eggs and sperm are released.

Conservation status

One species of callionymid, the St. Helena dragonet (Callionymus sanctaehelenae), which is endemic to the island of St. Helena in the South Atlantic, is currently listed by the IUCN as Critically Endangered. Some callionymids important to the aquarium trade, such as the mandarinfish (Synchiropus splendidus) and Repomucenus spp. that are important as food fishes, may also be at risk from overfishing, habitat destruction, and recruitment failure as a consequence of pollution or the creation of anoxic conditions that lead to hypoxia among larvae. No members of the Draconettidae are listed by the IUCN, but these fishes may be at risk from the effects of the deep trawling of their habitats.

Significance to humans

A number of dragonet species are important in the aquarium trade, such as the mandarinfish, and some species, such as Repomucenus spp., are taken directly or as bycatch in commercial or subsistence food fisheries, or for the production of fish meal. The Draconettidae may be taken incidentally by deep-trawling fishing vessels, but appear not to have any commercial significance to humans.

Species accounts

List of Species

Lancer dragonet

Paradiplogrammus bairdi

family

Callionymidae

taxonomy

Paradiplogrammus bairdi Jordan, 1888, off Pensacola, Florida, United States.

other common names

English: Coral dragonet; Spanish: Dragoncillo coralino.

physical characteristics

Total length 4.5 (11.4 cm). Sexually dimorphic; males are larger, have larger fins, extended dorsal fin, and more distinctive color patterns on body and fins. Body is elongate and scaleless in both sexes. Have 4 dorsal spines on first dorsal fin, 9 soft rays on second dorsal fin; 8 anal fin rays, but no spines. Color pattern is complex and varies between sexes. Dorsal half of body has marbling and mottling in various shades of brown, black, and white; white, roundish blotches between narrow brown bars on ventral half of body. First dorsal fin of male marked by yellow swirl and second dorsal fin with downward-pointing pattern of dark bands. Males also have blue concentric lines and rows of spots on first dorsal fin, blue bars with narrow orange margins on preopercle, orange spots, small blue lines and crescentlike markings on dorsal half of body, and blue spots around ventral half of eyes.

distribution

Western Atlantic, from Bermuda and southern Florida, United States, east and south to the Bahamas, south to the Lesser Antilles and northern South America, and west into the Gulf of Mexico.

habitat

Benthic; frequents sand patches on shallow reefs, rocky shorelines, and sea-grass flats at depths of 3.3–298.5 ft (1–91 m).

behavior

As with other dragonets, utilizes a relatively cryptic coloration to provide camouflage as it forages along the bottom. Social interactions, especially between males, can include the defense of territories or females, and are distinguished by erect fin displays.

feeding ecology and diet

Feeds upon small benthic invertebrates.

reproductive biology

Hermaphroditism has not been reported. Sexually dimorphic characters in males, mainly fin size, are used in reproductive behavior. Males initiate courtship by displaying erect fins towards females. Spawning is paired and occurs after short ascent into water column, where the eggs are fertilized. Eggs are pelagic, egg mass is likely buoyant and breaks up prior to hatching. Larvae generally typical of other dragonets.

conservation status

Not listed by the IUCN.

significance to humans

Collected for the aquarium trade. May be taken incidentally in bottom trawls by fishing vessels operating on offshore banks, but of no value as a food fish.

Richardson's dragonet

Repomucenus richardsonii

family

Callionymidae

taxonomy

Repomucenus richardsonii Bleeker, 1854, Nagasaki, Japan.

other common names

Japanese: Nezumi-gochi.

physical characteristics

Total length 6.7 (17 cm). Sexually dimorphic in character development. Body elongate and strongly depressed with broad, flattened head. Scales lacking. First dorsal fin with 4 spines; 9–10 soft rays on second, elongated dorsal fin. Anal fin has 9–10 soft rays. Relatively large pectoral and pelvic fins. Caudal fin elongate. Color pattern on body is light to medium brown. Males have three dark blotches on first dorsal fin and oblique dark lines along lower half of flank. Faint dark mottling on anal fin and ventral portion of caudal fin. Females and young males have large black mark on first dorsal fin; females also have three faint white spots on second dorsal fin. May live only as long as two years.

distribution

Northwestern Pacific, from central Japan west into the East China Sea.

habitat

Coastal bottoms of sand and mud.

behavior

Behavior not well known. Species is suited for movement, foraging, and crypsis on sandy or muddy bottoms. Social interactions include aggressive behavior between rival males, usually during courtship periods, with larger males dominating smaller ones. Aggressive behavior is characterized by display of erect fins during interactions.

feeding ecology and diet

Feeds mainly upon benthic invertebrates.

reproductive biology

Pronounced sexual dimorphism in color, body size, and fin development; males have greater body size as well as elongated fin spines and rays. These differences contribute toward reproductive success because of their value in defending against rival males or their signal function in attracting females. Courtship and spawning is paired, and commences with male displays of erect fins and results in pelagic spawning in water column. Eggs produced serially, likely spawned on daily basis with one or two spawning seasons (spring and early autumn). No evidence of hermaphroditism. Recruitment of larvae is also seasonal.

conservation status

Not listed by the IUCN. May be vulnerable or threatened by overfishing, habitat destruction, and pollution that causes anoxic conditions.

significance to humans

Occurs in both subsistence and commercial fisheries. Flesh favored in Japan. Also collected for the aquarium trade.

Mandarinfish

Synchiropus splendidus

family

Callionymidae

taxonomy

Synchiropus splendidus Herre, 1927, Bungau, Philippines.

other common names

Japanese: Nishiki-teguri.

physical characteristics

Total length about 3.1 in (8 cm). Sexually dimorphic; males larger than females and have larger dorsal fins. Small, somewhat elongated body lacks scales but has well-developed lateral line. Two dorsal fins, first with 4 spines and second with 8 dorsal rays. There are 6–8 soft rays on the anal fin. The preopercle has strong spine, but no spines present on operculum or suboperculum. Body coloration of vivid green or blue markings on ground color of orange, or rarely red.

distribution

Western Pacific and eastern Indian Ocean from the Philippines and Indonesia (Java), east to Pohnpei (Micronesia) and New Caledonia, south to northwestern Australia (Rowley Shoals) and to the southern Great Barrier Reef, and north to

the Ryukyu Islands of southern Japan. May also occur in Tonga.

habitat

Coral reefs on inshore reefs and in protected lagoons. Micro-habitat mainly coral heads, silty rubble, and even leaf litter. Ranges in depth 3.3–59 ft (1–18 m).

behavior

Generally solitary and cryptic within a home range. Emerges to feed during early morning, just before dusk, or in cloudy weather. Social interactions are relatively few and usually not aggressive.

feeding ecology and diet

Feeds upon small benthic invertebrates.

reproductive biology

Gonochoristic and polygynous, with a single male mating with more than one female daily. Courtship and spawning occurs during short period at dusk throughout most of the year. Females move to one or more specific areas before the onset of courtship. Males also move to and between these areas seeking females to court. Larger males dominate smaller males and prevent them from courting with females. Males use elaborate fin displays and circle females repeatedly during courtship. More than one bout of courtship may be necessary before a female is ready to spawn. Then, the pair rises slowly into the water column to spawn and fertilize a small batch (12–205) of pelagic eggs. After spawning, female returns to her home area to sleep, and male moves on to attempt to court and spawn with other females. Reported to have been bred in captivity. Larvae are pelagic.

conservation status

Not listed by the IUCN. May be vulnerable or threatened by overfishing, destructive fishing (including the use of cyanide), and destruction of habitat.

significance to humans

Important and highly prized aquarium fish harvested mainly in Southeast Asia and imported to the United States as part of the aquarium trade.

Draconett

Centrodraco insolitus

family

Draconettidae

taxonomy

Centrodraco insolitus McKay, 1971, off northwest Australia (17°17 S, 119°51 E, at a depth of 1,148 ft [350 m]).

other common names

None known.

physical characteristics

Total length about 5.1 (13 cm). Small, elongate, rounded body lacking scales. Lateral line grooved. Large eye and pointed snout. Two dorsal fins with three dorsal spines present on the first; the first dorsal spine is the longest. Both operculum and preoperculum have a single strong spine. Last dorsal and anal rays are branched, others are simple. Pectoral fin large and rounded. Pelvic fin elongate. Body pink with yellow blotches, and dark spots near pectoral fin and caudal peduncle.

distribution

Eastern Indian Ocean off coast of northwest Australia.

habitat

Deep-bottom rubble and sand to 1,040–1,148 ft (317–350 m) deep.

behavior

Nothing known.

feeding ecology and diet

Likely feeds upon small benthic invertebrates.

reproductive biology

Nothing known, but likely a pelagic spawning fish with paired courtship. Sexually dimorphic; males larger than females.

conservation status

Not listed by the IUCN. May be vulnerable to damage caused by deep trawling of habitats.

significance to humans

No direct significance. May be taken incidentally in deep-trawling fisheries.

Draconetta

Draconetta xenica

family

Draconettidae

taxonomy

Draconetta xenica Jordan and Fowler, 1903, Suruga Bay, Namazu, Japan.

other common names

Japanese: Inaka-numeri.

physical characteristics

Standard length 3.5 in (9 cm). Small, elongate, rounded body lacks scales but has grooved lateral line. Eye is large and snout pointed. There are two dorsal fins with three dorsal spines present on the first; first dorsal spine is the longest. Operculum and preoperculum have single strong spine. Last dorsal and anal rays branched, others are simple. Pectoral fins large and rounded, pelvic fins elongate. Body pink to whitish pink, with pink markings on dorsal, anal, and caudal fins.

distribution

Continental edges from East Africa to the Hawaiian Islands.

habitat

Deep-bottom rubble or sand.

behavior

Nothing known.

feeding ecology and diet

Probably feeds upon small benthic invertebrates.

reproductive biology

Largely unknown, but likely a pelagic spawning fish with paired courtship. Sexually dimorphic, males larger than females.

conservation status

Not listed by the IUCN. May be vulnerable to damage caused by deep-trawling of habitats.

significance to humans

No direct significance. May be taken incidentally in deep-trawling fisheries.

Resources

Books

Bohlke, J. E., and C. C. G. Chaplin. Fishes of the Bahamas and Adjacent Tropical Waters, 2nd edition. Austin: University of Texas Press, 1993.

Eschmeyer, W. N., ed. Catalog of Fishes, 3 vols. San Francisco: California Academy of Sciences, 1998.

Fricke, R. Revision of the Genus Synchiropus (Teleostei: Callionymidae). Braunschweig, Germany: J. Cramer, 1981.

——. Revision of the Indo-Pacific Genera and Species of the Dragonet Family Callionymidae (Teleostei). Braunschweig, Germany: J. Cramer, 1983.

Gloerfelt-Tarp, T., and P. J. Kailola. Trawled Fishes of Southern Indonesia and Northwestern Australia. Jakarta: Directorate General of Fisheries (Indonesia), German Agency for Technical Cooperation, Australian Development Assistance Bureau, 1984.

Helfman, G. S., B. B. Collette, and D. E. Facey. The Diversity of Fishes. Oxford: Blackwell Science, 1997.

Leis, J. M., and B. M. Carson-Ewart, eds. The Larvae of Indo-Pacific Coastal Fishes. Boston: Brill, 2000.

Masuda, H., K. Amaoka, C. Araga, T. Uyeno, and T. Yoshino, eds. The Fishes of the Japanese Archipelago. Tokyo: Tokai University Press, 1984.

Myers, R. F. Micronesian Reef Fishes. 3rd edition. Barrigada, Guam: Coral Graphics, 1999.

Nelson, J. S. Fishes of the World. 3rd edition. New York: John Wiley & Sons, 1994.

Randall, J. E., G. R. Allen, and R. C. Steene. Fishes of the Great Barrier Reef and Coral Sea, Revised and Expanded Edition. Honolulu: University of Hawaii Press, 1996.

Thresher, R. E. Reproduction in Reef Fishes. Neptune City, NJ: T.F.H. Publications, 1984.

Periodicals

Fricke, R., "Revision of the Family Draconettidae (Teleostei), with Descriptions of Two New Species and a New Subspecies." Journal of Natural History 26 (1992): 165–195.

Gosline, W. A. "A Reinterpretation of the Teleostean Fish Order Gobiosociformes." Proceedings of the California Academy of Sciences, 4, no. 37 (1970): 363–382.

Ikejima, K., and M. Shimizu. "Annual Reproductive Cycle and Sexual Dimorphism in the Dragonet, Repomucenus valenciennei, in Tokyo Bay, Japan." Ichthyological Research 45(1998): 157–164.

——. "Disappearance of a Spring Cohort in a Population of the Dragonet, Repomucenus valenciennei, with Spring and Autumn Spawning Peaks in Tokyo Bay, Japan." Ichthyological Research 46 (1999): 331–339.

——. "Sex Ratio in the Dragonet Repomucenus valenciennei." Ichthyological Research 46 (1999): 426–428.

Nakabo, T. "Comparative Osteology and Phylogenetic Relationships of the Dragonets (Pisces: Callionymidae) with Some Thoughts of Their Evolutionary History." Publications of the Seto Marine Biological Laboratory 28 (1983): 1–73.

——. "A New Species of the Genus Foetorepus (Callionymidae) from Southern Japan with a Revised Key to the Japanese Species of the Genus." Japanese Journal of Ichthyology 33 (1987): 335–341.

——. "Revision of the Genera of the Dragonets (Pisces: Callionymidae)." Publications of the Seto Marine Biological Laboratory 27 (1982): 77–131.

Randall, J. E. "Review of the Dragonets (Pisces: Callionymidae) of the Hawaiian Islands, with Descriptions of Two New Species." Pacific Science 53 (1999): 185–207.

Sadovy, Y., G. Mitcheson, and M. B. Rasotto. "Early Development of the Mandarinfish, Synchiropus splendidus (Callionymidae), with Notes on its Fishery and Potential for Culture." Aquarium Sciences and Conservation 3 (2001): 253–263.

Organizations

IUCN/SSC Coral Reef Fishes Specialist Group. International Marinelife Alliance-University of Guam Marine Laboratory, UOG Station, Mangilao, Guam 96913 USA. Phone: (671) 735-2187. Fax: (671) 734-6767. E-mail: donaldsn@uog9.uog.edu Web site: <http://www.iucn.org/themes/ssc/sgs/sgs.htm>

Terry J. Donaldson, PhD